This invention relates to a film drive for a motion-picture apparatus. More particularly this invention concerns a film advance for a motion-picture camera or projector.
In both a motion-picture camera and a motion-picture projector it is necessary to drive the film in at least two separate manners: it must be able to move intermittently during exposure or projection in synchronism with appropriate shutter arrangements, and it must be able to move continuously for loading and/or rewinding. Typically the displacement rate during continuous displacement can be no greater than two to three times the normal advance speed during intermittent displacement.
In most movie projectors and cameras the complicatd intermittent-drive arrangement is simply disconnected and an auxiliary continuous drive is connected up for rewinding or loading the film. Such provision of two separate drives considerably increases the cost of the unit as well as its size. Furthermore, after the film has been rewound or advanced continuously it is necessary to orient it again properly behind the shutter, as the sprocket wheel which serves intermittently to drive the film and to synchronize the frames with the shutter action has been disengaged.